1. Field
This invention pertains to locking systems useful to position flow control devices in well flow conduits.
2. Information
A number of locking systems have been developed which employ landing nipples spaced apart in well flow conduits and lock mandrels, with flow controls connected, which locate, releasably lock and seal in a selected one of the landing nipples. The landing nipples used in existing systems either contain a restriction or a "square shoulder" to enable selection and location of a particular landing nipple in a well conduit in which the lock mandrel is to be operated to lock and seal. A square shoulder is created by a surface perpendicular to and intersecting the longitudinal flow passage through a landing nipple. A restriction in a landing nipple undesirably reduces the through flow passage area to create a shoulder on which a lock mandrel may locate. A very limited number of restricted bore landing nipples can be utilized in a well flow conduit. If the landing nipple is "full bore" and not restricted, it usually has profiled recesses in which the lock mandrel may locate. Lock mandrels and well tools moved downwardly or upwardly through landing nipples often hang on restricting shoulders which may be eroded and create flow turbulence that possibly aids undesirable deposition of hard scale in the landing nipple.